According to the new US National Defense Strategy, the United States places primary responsibility for “deterring” North Korea on the Republic of Korea.
A Brief Overview of the Strategy
This is a continuation of the doctrine in which the US understands that its resources and capabilities are grand but not infinite. Therefore, it must first set its own house in order, or at least establish order in the Western Hemisphere. Afterwards, it can return better prepared for the upcoming struggle for global leadership.
Korea’s Place in the New Document
As it was in the 2022 version of the National Security Strategy published by the White House in December 2025, the 2026 NDS does not mention the denuclearisation of North Korea. In general, only a couple of paragraphs with trivial content were dedicated to North Korea. “The DPRK poses a direct military threat to the Republic of Korea (ROK) as well as to Japan, both of which are U.S. treaty allies. Although many of North Korea’s large conventional forces are aged or poorly maintained, South Korea must stay vigilant against the threat of a North Korean invasion.” “North Korea’s missile forces are also capable of striking targets in the ROK and Japan with conventional and nuclear weapons as well as other weapons of mass destruction… These forces are growing in size and sophistication, and they present a clear and present danger of nuclear attack on the American homeland.”
The main point regarding the ROK in the strategy boils down to the following: “With its powerful military, supported by high defense spending, a robust defense industry, and mandatory conscription, South Korea is capable of taking primary responsibility for deterring North Korea with critical but more limited U.S. support.” Such a position aligns with America’s interests in “modernising” the US armed forces on the Korean Peninsula.
What does the phrase “critical but more limited support” mean? According to analysts, it signifies America’s commitment to using its nuclear weapons under the framework of “extended deterrence” against North Korea, taking into account the ROK’s superiority in conventional weapons. The term “extended deterrence” per se is absent from the text, which is a concern for conservatives. In last year’s joint fact sheet outlining bilateral security and trade agreements, the Trump administration officially reaffirmed its commitment to providing extended deterrence using the full range of its capabilities, including nuclear assets. However, in other areas, the ROK Army is strong enough and capable of dealing with the DPRK threat on its own.
The passage about the desire to “modernize” the US force deployment in Korea is linked to what has already been noted in discussions about a “reversed map.” Washington may adjust the mission, operational scale, and composition of the 28,500-strong US Armed Forces in Korea. It could reorient them from countering the DPRK to addressing regional crises, including the Taiwan situation. The US likely wants to reduce the number of ground troops and increase the size of the Air Force and Navy. This would optimize the force configuration for contingencies related to deterring China.
And the First Steps Towards Implementing the New Document
The results of the visit to Seoul by US Under Secretary of Defense for Policy Elbridge Colby can be considered as such a step. He stated that South Korea is an exemplary ally that has undertaken to comply with the global standard of military spending at 3.5% of GDP.
During his visit on January 26, Colby met with South Korean Minister of Defense Ahn Gyu-back, National Security Advisor Wi Sung-lac, and Foreign Minister Cho Hyun. The sides held in-depth discussions on issues relevant to the US-ROK alliance. These included the security situation on the Korean Peninsula, ROK plans to build its own nuclear-powered submarines, the transfer of wartime operational control (OPCON), strengthening defense capabilities, etc. Ahn highly praised the agreements reached last year by the leaders of the two states and the outcomes of the 57th Security Consultative Meeting (SCM), having described them as turning points in the development of the Seoul-Washington alliance. In response, Colby expressed commitment to continuing efforts to strengthen defense cooperation.
The parties agreed that cooperation within the nuclear submarine construction program would enhance the ROK’s defense capabilities. They viewed it as an important step in strengthening the military alliance and agreed on making joint efforts in this direction.
Seoul’s Reaction
In general, the official authorities of South Korea welcomed the new concept. This is because “President Lee Jae Myung seeks to strengthen South Korea’s independent defense potential and reclaim the ROK’s wartime operational control (OPCON)” before his presidential term comes to an end.
Commenting on the US defense strategy, President Lee stated that achieving “self-sufficient national defense” is the most fundamental principle of the country’s military policy. “In the face of an unstable international security situation, achieving self-sufficient defense is the most basic principle,” Lee Jae Myung wrote in his social media account on X. It is impossible to imagine that the ROK cannot defend itself when its defense spending is 1.4 times the GDP of North Korea and it possesses the world’s fifth-largest military power. “Reliable self-sufficient defense and peace on the Korean Peninsula will ensure sustainable economic growth,” Lee emphasised.
A representative of the Ministry of Defense also noted, “Our government takes note of how the US government assessed our capabilities and determination to play a more leading role in ensuring the security of the Korean Peninsula in 2026.” “While maintaining a reliable combined defense, our military will closely cooperate with the United States for the South Korea-US alliance to transform into a future-oriented, comprehensive strategic alliance.”
Professor Nam Chang-hee of International Politics at Inha University believes that if “US commitments under the nuclear umbrella weaken, South Korea will have two options: move towards nuclear armament or sharply increase its conventional armed forces through means such as the Hyunmoo-5 missile, which is powerful enough to create a balance of terror in relations with Pyongyang.”
The centre-right The Korea Times, however, notes that “the wording calling on Korea to take ‘primary responsibility,’ while the US offers only limited support, indicates higher costs for Seoul.” According to the author of the article, the US alliance with Seoul is entering a period of change. The “America First” defense strategy is defined as a strategy aimed at protecting the US territory and ensuring military and commercial access to strategically important facilities in the Western Hemisphere, including Greenland and the Panama Canal. Within this framework, allies like Korea will bear primary responsibility for conventional deterrence.
The rightists are also apprehensive about the absence of references to the US commitment to North Korea’s denuclearization. As the author has already pinpointed, Seoul is stuck in the past, trying to push an agenda that is viewed critically even in the US. Nevertheless, “Seoul will need to persuade Washington to acknowledge its pragmatic approach, while simultaneously encouraging its alliance partner to support an engagement-based path to denuclearization… Furthermore, both sides must reaffirm that denuclearization remains the ultimate goal should dialogue between the United States and North Korea resume.”
The media which are even more conservative put it harsher. The new strategy is “not just an update of wording or force posture. It is an official acknowledgment of America’s strategic fatigue. By elevating the Western Hemisphere to the status of a near-sacred defense priority and demanding greater regional self-sufficiency elsewhere, Washington has revised its hierarchy of commitments. South Korea remains an important country, but no longer an indispensable one.” They remind that Colby who visited the country was the first to openly doubt whether any US president would risk American cities for Seoul. Praise from his lips looks hazardous.
Supporters of the traditional US-ROK alliance state directly that “now the Korean Peninsula is less a place to be liberated after a Northern invasion and more a permanent cork blocking the breakout of Chinese naval forces. North Korea recedes into the background. China sets the geometry.” At the same time, the readiness of the ROK Army to deter at least the North is declining. The number of armed forces has allegedly shrunk to about 450,000. Funding is scarce, and constant purges and reorganizations hit manageability and morale.
In other words, the new US approach to the ROK increasingly differs from the traditional one. However, the ROK is still hitching its wagon to Washington’s policy.
Konstantin Asmolov, PhD in History, Leading Research Fellow at the Centre for Korean Studies, Institute of China and Contemporary Asia, Russian Academy of Sciences
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